I feel like many slang words are just shortened versions of the original word.

from the following, my guess would be that we go from bitcoin to bicoy(BiK-Oi) to something like Boy with a very gentle soft 'i' sound between the 'B' and the 'oi' sound, like Bi-Oi, most likely eventually resting at 'boy' without a strong 'y' at the end.

Taken from John McWhorter's Story to Human Language Course Guide

III. Typical sound change processes.A. Assimilation. Many of these changes seem to us to be “sloppy”speaking. For example, in early Latin, the word for impossible isinpossibilis, but in later Latin, the word was impossibilis. The nchanged to an m because the m sound is closer to a p than n. Thisprocess is called assimilation. Over time, laziness created a newword—the one we borrowed from Latin that is so proper to us today!in-possibilis > im-possibilisB. Consonant weakening. Similarly, over time, consonants tend to weakenand even disappear.1. In Latin, the word for ripe was maturus. In Old Spanish, the wordwas pronounced the way it is written today: maduro; the tweakened into a d, and the s at the end vanished. But in CastillianSpanish today, the word is actually pronounced “mathuro,” withthe soft kind of th in mother. In Old French, the word was similar,pronounced “mathur,” but since then, the th sound has dropped outcompletely, and the word is just mûr.

I like to refer to all money, but BTC in particular as Coin... I probably played too much Mario as a kid WTF was he going to do with all those coins he was hoarding anyways? Not like I ever saw a shop in the Mushroom Kingdom.